The cause of low back pain in populations of professional drivers is uncertain. A literature review revealed factors that seem to be associated with low back pain (e.g. physical factors: exposure to whole body-vibration, prolonged sitting posture, frequent lifting, pushing and pulling, lack of physical fitness; psychosocial factors: job satisfaction or stress; individual factors: age, gender, anthropometrics, tobacco, alcohol consumption, etc.). This thesis investigates the occurrence of back pain in professional car drivers – a group found to be not focussed upon in previous epidemiological studies. The thesis seeks to advance understanding of response relationships between risk factors and low back pain in populations of car drivers (209 taxi drivers and 365 police drivers) and 485 non-drivers. A longitudinal study with cross-sectional baseline combined with field measurement of driving in selected vehicles was performed to investigate the occurrence of musculoskeletal problems (mainly low back pain) and the relationship between risk factors and low back pain experienced for at least one day during the past 12 months in the two populations of professional drivers (taxi drivers and police drivers) and professional non-drivers. The cross-sectional baseline of the longitudinal study revealed that 45% (38.3-51.7%) of taxi drivers, 53% (48-58.6%)of police drivers and 46% (41-50.1%) of police non-drivers reported low back pain for at least one day during the past 12-months (p = 0.09). The prevalence of low back pain in the non-driving population of police employees fell within prevalence range reported by professional car drivers in this study and in previous epidemiological studies. The cross-sectional study revealed risk factors associated with the prevalence of low back pain (i.e., stature, previous physical demands, increased psychosomatic distress, daily and cumulative driving in taxi drivers; age, lifting, bending, increase psychosomatic distress in police drivers; stature, bending, increased psychosomatic distress in police non-drivers). Measurements of whole-body vibration in selected taxi and police vehicles revealed frequencyweighted accelerations in the dominant vibration direction (i.e., z-axis) to be 0.47 ms-2 r.m.s. in taxi vehicles and 0.58 ms-2 r.m.s. in police vehicles. A study of cumulative exposure to whole-body vibration in a group of taxi drivers pointed to a possible overestimation of their self-estimated duration of vibration exposure by 31% on average. The longitudinal study revealed a lower incidence of low back pain in taxi drivers than in both police drivers and police non-drivers (p = 0.02). The difference might be attributed to a different approach to low back pain in taxi drivers who lose income if unable to work. An alternative explanation for increased low back pain among police employees could be that taxi drivers with low back pain leave their profession and were excluded from the follow-up study – a healthy worker effect. The longitudinal study revealed that increased psychosomatic distress was a risk factor associated with the development of new episodes of low back pain in all three of the studied populations (i.e. taxi drivers and police drivers and non-drivers). In police drivers, increased daily duration of driving was a risk factor for the development of low back pain. Although the results point to increased incidence of low back pain with increasing duration of daily driving, non-drivers were at a similar risk of developing of low back pain. Plausible explanations for this finding include ergonomic factors that were present for both the drivers and the non-drivers (e.g., the duration of sitting or duration in a constrained posture) and the presence of other risk factors not investigated in the study but associated with increased incidence of low back pain in non-drivers.